1.\" 2.\" Copyright (c) 2009 Lawrence Stewart <lstewart@FreeBSD.org> 3.\" Copyright (c) 2011 The FreeBSD Foundation 4.\" All rights reserved. 5.\" 6.\" Portions of this documentation were written at the Centre for Advanced 7.\" Internet Architectures, Swinburne University of Technology, Melbourne, 8.\" Australia by Lawrence Stewart under sponsorship from the FreeBSD Foundation. 9.\" 10.\" Redistribution and use in source and binary forms, with or without 11.\" modification, are permitted provided that the following conditions 12.\" are met: 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in the 17.\" documentation and/or other materials provided with the distribution. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR 23.\" ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.Dd May 13, 2021 32.Dt CC_NEWRENO 4 33.Os 34.Sh NAME 35.Nm cc_newreno 36.Nd NewReno Congestion Control Algorithm 37.Sh SYNOPSIS 38.In netinet/cc/cc_newreno.h 39.Sh DESCRIPTION 40The NewReno congestion control algorithm is the default for TCP. 41Details about the algorithm can be found in RFC5681. 42.Sh Socket Options 43The 44.Nm 45module supports a number of socket options under TCP_CCALGOOPT (refer to 46.Xr tcp 4 47and 48.Xr mod_cc 9 for details) 49which can 50be set with 51.Xr setsockopt 2 52and tested with 53.Xr getsockopt 2 . 54The 55.Nm 56socket options use this structure defined in 57<sys/netinet/cc/cc_newreno.h>: 58.Bd -literal 59struct cc_newreno_opts { 60 int name; 61 uint32_t val; 62} 63.Ed 64.Bl -tag -width ".Va CC_NEWRENO_BETA_ECN" 65.It Va CC_NEWRENO_BETA 66Multiplicative window decrease factor, specified as a percentage, applied to 67the congestion window in response to a congestion signal per: cwnd = (cwnd * 68CC_NEWRENO_BETA) / 100. 69Default is 50. 70.It Va CC_NEWRENO_BETA_ECN 71Multiplicative window decrease factor, specified as a percentage, applied to 72the congestion window in response to an ECN congestion signal when 73.Va net.inet.tcp.cc.abe=1 74per: cwnd = (cwnd * CC_NEWRENO_BETA_ECN) / 100. 75Default is 80. 76.El 77.Sh MIB Variables 78The algorithm exposes these variables in the 79.Va net.inet.tcp.cc.newreno 80branch of the 81.Xr sysctl 3 82MIB: 83.Bl -tag -width ".Va beta_ecn" 84.It Va beta 85Multiplicative window decrease factor, specified as a percentage, applied to 86the congestion window in response to a congestion signal per: cwnd = (cwnd * 87beta) / 100. 88Default is 50. 89.It Va beta_ecn 90Multiplicative window decrease factor, specified as a percentage, applied to 91the congestion window in response to an ECN congestion signal when 92.Va net.inet.tcp.cc.abe=1 93per: cwnd = (cwnd * beta_ecn) / 100. 94Default is 80. 95.El 96.Sh SEE ALSO 97.Xr cc_cdg 4 , 98.Xr cc_chd 4 , 99.Xr cc_cubic 4 , 100.Xr cc_dctcp 4 , 101.Xr cc_hd 4 , 102.Xr cc_htcp 4 , 103.Xr cc_vegas 4 , 104.Xr mod_cc 4 , 105.Xr tcp 4 , 106.Xr mod_cc 9 107.Rs 108.%A "Mark Allman" 109.%A "Vern Paxson" 110.%A "Ethan Blanton" 111.%T "TCP Congestion Control" 112.%O "RFC 5681" 113.Re 114.Rs 115.%A "Naeem Khademi" 116.%A "Michael Welzl" 117.%A "Grenville Armitage" 118.%A "Gorry Fairhurst" 119.%T "TCP Alternative Backoff with ECN (ABE)" 120.%O "RFC 8511" 121.Re 122.Sh ACKNOWLEDGEMENTS 123Development and testing of this software were made possible in part by grants 124from the FreeBSD Foundation and Cisco University Research Program Fund at 125Community Foundation Silicon Valley. 126.Sh HISTORY 127The 128.Nm 129congestion control algorithm first appeared in its modular form in 130.Fx 9.0 . 131.Pp 132The module was first released in 2007 by James Healy and Lawrence Stewart whilst 133working on the NewTCP research project at Swinburne University of Technology's 134Centre for Advanced Internet Architectures, Melbourne, Australia, which was made 135possible in part by a grant from the Cisco University Research Program Fund at 136Community Foundation Silicon Valley. 137More details are available at: 138.Pp 139http://caia.swin.edu.au/urp/newtcp/ 140.Sh AUTHORS 141.An -nosplit 142The 143.Nm 144congestion control module was written by 145.An James Healy Aq Mt jimmy@deefa.com , 146.An Lawrence Stewart Aq Mt lstewart@FreeBSD.org 147and 148.An David Hayes Aq Mt david.hayes@ieee.org . 149.Pp 150Support for TCP ABE was added by 151.An Tom Jones Aq Mt tj@enoti.me . 152.Pp 153This manual page was written by 154.An Lawrence Stewart Aq Mt lstewart@FreeBSD.org . 155